Field of the Invention
Embodiments of the present invention generally relate to distributed power systems and, more particularly, to a method and apparatus for monitoring maximum power point tracking.
Description of the Related Art
Distributed power systems typically comprise a power source that generates direct current (DC) power, a power converter, and a controller. The power source may be a distributed generator such as a photovoltaic (PV) module, a wind turbine, a hydroelectric generator, fuel cell, and the like. The power converter may convert the DC power into alternating current (AC) power, which may be coupled directly to the AC power grid.
One indicator of the efficiency at which the distributed generator is operating is represented in a graph of current versus voltage also referred to as an I-V curve or I-V characteristic. The point on the curve associated with the voltage and current values that result in maximum power is known as the maximum power point (MPP). To ensure that the distributed generator is running at peak efficiency, a technique is used to maintain the distributed generator at this maximum power point, i.e., a maximum power point tracking (MPPT) function implemented by a coupled power converter. Ideally, the MPPT function ensures a maximum power from the distributed generator as power output may vary, for example as a result from degradation or shading of a PV module. The MPPT function varies internal electronic controls of the power converter to drive the distributed generator to its MPP. Since the MPP shifts with external factors (PV panel degradation, shading, and the like), it is important that MPPT operates efficiently to maintain the distributed generator at its MPP.
Therefore, there is a need in the art for monitoring the MPPT performance of a device performing MPPT.